The present invention relates to a bipolar medical instrument comprising a tubular shaft with at least two jaw parts, which are arranged movably, one relative to the other, at the distal end of the tubular shaft and which are coupled via a joint, and each of which forms a work electrode of different polarity, with a separate current conductor being associated to each jaw part, one of such current conductors being constituted by an axially movable force transmission element that is arranged in the tubular shaft and is force-lockingly coupled to at least one of the jaw parts.
An instrument of this kind is known from DE 196 08 716 C1.
In minimally invasive surgery, an instrument of the before-mentioned kind is used for performing endoscopic operations in human or animal bodies.
The two jaw parts at the distal end of the tubular shaft are connected one with the other via a joint so that they can be opened and closed by actuation of a handle provided on the proximal end of the tubular shaft. Depending on the surgical application of such an instrument, the jaw parts are configured as cutting tools with cutting edges for cutting off tissue in the body, or as grasping tools and then with flatly abutting surfaces for grasping any cut-off tissue with the jaw parts in order to remove it from the body, or for holding an organ or a vessel so as to move it out of the operation field. Moreover, the jaw parts may have a combination of functions, namely a cutting and a grasping function.
At least one of the two jaw parts is connected with the tubular shaft in articulated fashion, while the other jaw part is connected with the tubular shaft either rigidly, or likewise in articulated fashion.
The before-mentioned kind of a medical instrument further provides that the two jaw parts each form a work electrode of different polarity that can be supplied with high-frequency (HF) current. Accordingly, each of the two jaw parts can be separately connected to one pole of a HF voltage source. By supplying the two jaw parts with a bipolar HF current it is possible, on the one hand, to increase the cutting effect by the thermal effect of the HF current in the tissue, if the tools are configured as cutting tools, while on the other hand, if they are configured as grasping tools, any tissue grasped between the jaw parts can be coagulated, and haemorrhages can be stopped, by the heat developed.
It is always a problem with such bipolar instruments to achieve a sufficient electric insulation effect between the two jaw parts in the region of the joint where the two jaw parts are in contact one with the other also in the open condition. When supplying the jaw parts with HF current, they must be electrically isolated as the two jaw parts are connected to different potentials. The problem of isolating the two jaw parts electrically is the greater the smaller such an instrument is configured in the region of the jaw parts and, thus, in the region of the joint. Small overall widths of the instrument in the area of the jaw parts are, however, especially important in minimally invasive surgery.
In the case of the instrument known from the before-mentioned DE 196 08 716 C1, the two jaw parts consist completely of metal and are, therefore, electrically conductive over their entire body. A force transmission element in the form of a push-and-pull rod is coupled with the two movable jaw parts via an articulated lever arrangement. The push-and-pull rod serves additionally as current conductor connecting one of the two jaw parts to the one pole of a HF voltage source.
In the case of this known instrument, the electric isolation of the two jaw parts is accomplished by ceramic elements which are inserted into the otherwise metallic joint of the two jaw parts and which, therefore, are themselves part of the joint. This way of electrically isolating the two jaw parts one from the other in the area of the joint provides, however, the disadvantage that when miniaturizing that instrument the size of the ceramic elements must be reduced as well. Since usually the HF frequency supplied to the jaw parts is in the range of 2.5 kV, this means that a voltage puncture may occur through the ceramic element in case that the size of the ceramic elements is reduced. Another disadvantage of the ceramic elements lies in the fact that the installed ceramic elements are subjected to frictional forces due to the movement of the jaw parts so that they may be crushed in the course of time. Further, it is a disadvantage of the configuration of the known instrument that the number of parts of the forceps in the region of the jaw parts and, thus, the constructional input and the cost of production of that known instrument, are undesirably increased.
From DE 43 12 284 A1 there has been further known a bipolar medical instrument where the jaw parts are completely made from a plastic material and stripped sections of current conductors are embedded in such plastic material. The jaw parts are configured as cutting members, consisting of plastic material, and work electrodes are embedded in the plastic material of the jaw parts. It is a disadvantage of that configuration that the current supply to the jaw parts is realized through separate electric conductors that are run through the push-and-pull rod in insulated fashion. The push-and-pull rod as such, therefore, does not serve as a current conductor in the case of these forceps. Consequently, this instrument is also connected with the disadvantage that the number of parts required is increased by the additional current conductors. An additional disadvantage lies in the fact that the end portions of the current conductors, that extend into the plastic material of the jaw parts, are subjected to bending stresses every time the jaw parts are opened or closed, so that the end portions may break in the course of time whereby the current flow to the electrodes would be interrupted.
An instrument similar to the instrument described above is known from WO 99/40861. This known medical bipolar instrument comprises, at the distal end of the shaft, two jaw parts that are movable one relative to the other, with one jaw part being movable, while the other jaw part is immovable. The movable jaw part is biased by means of a spring into a position in which it is pivoted away from the immovable jaw part, i.e. in which it occupies its open position. The actuating mechanism for the movable jaw part consists of a tubular shaft enclosing the shaft, which can be displaced in axial direction and which, when displaced in the distal direction, comes to slide onto the outer surface of the movable jaw part, whereby the latter is pressed against the immovable jaw part. The movable jaw part is coupled in articulated fashion with the immovable jaw part via a pin joint. The two jaw parts are again completely made from a plastic material, with metallic electrodes fastened to the plastic material. The current supply to the electrodes is again realized by individual conductors connected to the electrodes. Accordingly, this instrument is again connected with the disadvantage that the number of parts required is increased as a result of the additional current conductors and that the current supply lines, implemented as wires, are subjected to bending stresses during opening and closing of the jaw parts.
It is, therefore, the object of the present invention to improve a bipolar medical instrument of the before-mentioned type so that safe insulation of the jaw parts in the region of their joint is achieved without an increase in the number of parts and with lower constructional input.
According to the invention, this object is achieved with a bipolar instrument, comprising
a tubular shaft having a proximal end and a distal end;
at least two jaw parts arranged movably, one relative to the other, at said distal end of said tubular shaft and coupled one to the other via a joint, each of said at least two jaw parts forming a work electrode of different polarity;
a separate current line for each of said at least two jaw parts, one of such current lines being constituted by an axially movable force transmission element arranged in said tubular shaft and force-lockingly connected to at least one of said jaw parts,
wherein at least one of said jaw parts comprises, at least in the region of said joint, a single-piece main body made from an electrically insulating material on which an electrically conductive jaw part insert is fastened, which forms said respective work electrode and which is connected, in an electrically conductive fashion, to said respective associated current line.
It is, thus, provided according to the invention to equip at least one of the jaw parts with an electrically insulating single-piece main body. Such an electrically insulating main body may consist, for example, of a hard plastic material so that the instrument will meet the high demands placed on it in terms of stability in the area of its jaw parts. By having the connecting joint between the first jaw part and the second jaw part now arranged in the area of the single-piece insulating main body, electric isolation of the two jaw parts one from the other is now accomplished without any additional components, such as ceramic elements. The main body, being made from an insulating material, may be made particularly solid so that the stability of that jaw part and the stability of the joint are as high as if the jaw parts were completely made from metal. This configuration is suited for instruments where both jaw parts are movable, and also for instruments where one jaw part only is movable. The pin of the joint, which connects the two jaw parts one with the other in articulated fashion, may even be made from metal in the configuration of the invention, since any current transfer to the other jaw part is safely prevented by the main body consisting of an insulating material.
If only one jaw part is made movable the at least one jaw part that comprises the main body made from an electrically insulating material may be the immovable jaw part, for example, whereas the other movable jaw part, which is frictionally coupled to the force transmission element, may consist of metal in its entirety without any current transfer occurring from that movable jaw part to the immovable jaw part through the joint. It is possible in this way to realize the desired current flow between the force transmission element and the movable jaw part, without any additional connection measures. While in the case of the instrument known from DE 196 08 716 C1 an insulating ceramic element is also required in the area where the push-and-pull rod is hinged on the articulated lever arrangement, the present invention can do without any such additional insulating element. All in all, an especially simple structure of the instrument, requiring only a small number of parts, is achieved by the invention.
The object underlying the present invention is thus perfectly achieved.
According to a preferred embodiment, the main body comprises a distal section in which the jaw part insert, being arranged in that section, is enclosed on its outside in insulated fashion.
It is an advantage of this configuration that the HF current will come to act only on tissue that gets into contact with the working surface of the jaw part insert, while any tissue not involved in the operation, that may get into contact with the outside of the jaw part in the operation area, will not be impaired by the HF current. This permits the treatment of tissue with HF current to be carried out in a much more selective way.
According to another preferred embodiment, the jaw part insert is connected with the main body in friction-locking and in positive fashion.
The combined force-locking and positive connection provides the advantage that the jaw part insert is safely anchored on the main body. xe2x80x9cForce-locking and positive connectionxe2x80x9d is to be understood in this case as sort of an interlocking connection between the jaw part insert and the main body that prevents the jaw part insert from being lifted off the main body. Such a connection may be implemented, for example, in the form of a T-shaped groove in the main body and a complementary T-shaped key on the jaw part insert. A force-locking and positive connection provides the particular advantage of high mechanical durability, which cannot be achieved by a jaw part insert cast into or embedded in the main body, as provided by the prior art. In addition, such a connection is especially temperature-resistant as it does without any connection of substances, as would occur if the connection were realized by cementing.
From the manufacturing point of view it is especially preferred if the jaw part insert is fastened on the main body by a dovetail connection.
The jaw part insert may be additionally secured on its proximal end by means of a screw or a pin to prevent relative movement with respect to the main body.
According to a further preferred embodiment, one of the jaw parts is rigidly connected with the tubular shaft, and at least that jaw part comprises the main body consisting of an electrically insulating material.
As has been mentioned before, this provides the advantage that the movable jaw part may be completely made from metal, in which case the current transfer from the force transmission element to the movable jaw part can be accomplished in a very simple way, constructionally. Since the immovable jaw part is fastened on the tubular shaft and since, accordingly, its proximal section corresponds to the diameter of the tubular shaft, in terms of dimension, this feature provides the additional advantage that the immovable jaw part can be configured to comprise a main body made from an insulating material with especially high rigidity.
It is especially preferred if each of the two jaw parts comprises a main body made from an electrically insulating material, with an electrically conductive jaw part insert, forming the respective work electrode of the jaw part, arranged thereon.
This feature provides the particular advantage that both jaw parts are completely insulated on their outside, at least in their proximal area, so that the HF current is applied only to such tissue that gets into contact with the jaw part inserts.
According to a further preferred embodiment, the tubular shaft forms the other current line, and the latter is connected with the other jaw part in electrically conductive fashion, while being insulated from the force transmission element.
This feature, which is known as such, contributes still further toward simplifying the structure of the forceps according to the invention, because no additional conductors are necessary for the current supply to the two jaw parts.
According to a further preferred embodiment, the main body made from insulating material is provided at least in that jaw part which is connected with the force transmission element, in which case the force transmission element is hinged on a proximal section of the main body on which an electrically conductive connection element is provided which then connects the force transmission element with the respective jaw part insert in electrically conductive fashion.
This embodiment, according to which the movable jaw part comprises a main body made from an electrically insulating material, is likewise advantageous. For, the proximal section of the main body made from an insulating material is bridged by the electrically conductive connection element, for the purpose of transferring the current to the jaw part insert, without the electrically conductive connection element being subjected to bending stresses during movement of the jaw part; this is so because an articulated, rather than a flexible, connection exists between the force transmission element and the connection element.
It is preferred in this connection if a pivot pin of the joint connecting the first jaw part with the second jaw part passes through the connection element.
The advantage of this arrangement lies in the fact that the connection element strengthens the pivot pin and prevents the pivot pin from working itself free in the non-metallic proximal section of the two jaw parts. The pivot pin of the joint may be electrically insulated, for example by a corresponding jacket, in order to ensure, in case the two ends of the pivot pin are exposed, that the entire outside of the instrument is insulated in the region of the joint of the jaw parts.
According to a further preferred embodiment, the force transmission element is connected to a current supply via a spring-loaded contact in a proximal region of the force transmission element.
Current transmission by means of a spring-loaded contact provides the advantage of a constructionally especially simple power supply to the axially movable force transmission element, which offers the additional advantage that the power supply as such can be stationarily arranged on the instrument itself, for example in the form of a connector housing or a connector socket for a cable.
According to certain preferred further developments of that feature, the spring-loaded contact is a wiper contact, for example an elongated metallic element in the form of a leaf spring, and/or the contact comprises an element, especially a ball, which is spring-loaded toward the force transmission element. This latter configuration provides the additional advantage that considerably less friction occurs between the ball and the force transmission element.
According to another preferred embodiment, the jaw part insert of the immovable jaw part, being connected with the tubular shaft, is connected in electrically conductive fashion with the tubular shaft via an electrically conductive wire element which is embedded in the proximal section of the second main body.
By having the element embedded in the main body of the immovable jaw part, this feature leads, advantageously, to an electrically conductive connection between the tubular shaft and the jaw part insert of the immovable jaw part, which is insulated from the force transmission element. Given the fact that the jaw part is immovable, the wire element is not subjected to bending stresses. In addition, the wire element, being embedded in the main body of the immovable jaw part, is protected from mechanical influences.
According to a further preferred embodiment, a proximal section of the second jaw part comprises a recessed portion with two legs extending in longitudinal direction, with the main body of the first jaw part being arranged between such legs and being connected with the legs in articulated fashion.
This feature provides the advantage that an especially slim, space-saving structure and a case-like connection between the two jaw parts is achieved.
According to a further preferred embodiment, a proximal section of the first jaw part comprises a fork section which is engaged by the force transmission element.
This feature provides the additional advantage that hinging the force transmission element on the movable jaw part can be accomplished in an especially sturdy and little space-consuming way.
According to a further preferred embodiment, the main body of the one jaw part and/or the main body of the second jaw part, if necessary, consist of a hard, especially a temperature-resistant plastic material.
This feature permits especially high stability of the main bodies of the jaw parts to be achieved. If in addition the plastic material is selected to be temperature-resistant, this provides the advantage that the jaw parts can be sterilized in an autoclave. Such hard plastic materials are generally known and available.
The forceps according to the invention can be configured as a grasping instrument, by giving mutually opposite inner surfaces of the work electrodes a planar surface, or as a cutting instrument, by configuring the mutually opposite inner faces of the work electrodes as cutting elements. The configurations according to the invention described above can be used with advantage for both types of instruments. When the work electrodes are configured as grasping tools, it is further preferred to give them complementary V-shaped cross-sections, whereby the tissue to be grasped is prevented from escaping laterally.
In cases where the work electrodes are configured as cutting elements, it is preferred if the inner surface of the one work electrode is provided with a notch extending in longitudinal direction, and the inner surface of the other work electrode is provided with a cutting edge coacting with that notch in cutting fashion.
This embodiment of the jaw parts is similar to that of anvil pliers which permit high cutting forces to be transferred to the tissue to be cut.
Other advantages will become apparent from the description that follows, and from the attached drawing.
It is understood that the features recited above and those yet to be explained below can be used not only in the respective combination indicated, but also in other combinations or in isolation, without leaving the context of the present invention.